3

我有两个列表列表，其中包含一些像这样的 3D 坐标（例如）：

a = [[1, 2, 3], [4, 5, 6], [4, 2, 3]]
b[0] = [[11, 22, 3], [12, 34, 6], [41, 2, 34], [198, 213, 536], [1198, 1123, 1156]]
b[1] = [[11, 22, 3], [42, 25, 64], [43, 45, 23]]
b[2] = [[3, 532, 23], [4, 5, 6], [98, 23, 56], [918, 231, 526]]
b[n] = [[11, 22, 3], [42, 54, 36], [41, 2432, 34]]

查找“b”的任何元素是否在列表“a”中具有任何坐标的快速方法是什么？例如，在给定的示例中，“a[2]”和“b[2][1]”是相同的，所以我希望程序返回“true”。

4

4 回答 4

4

将最里面的列表转换b成一个集合（s），然后迭代a检查是否a存在任何项目s。

tot_items_b = sum(1 for x in b for y in x) #total items in b

集合提供O(1)查找，因此整体复杂性将是：

O(max(len(a), tot_items_b))

def func(a, b):
   #sets can't contain mutable items, so convert lists to tuple while storing

   s = set(tuple(y) for x in b for y in x)
   #s is set([(41, 2, 34), (98, 23, 56), (42, 25, 64),...])

   return any(tuple(item) in s for item in a)

演示：

>>> a = [[1, 2, 3], [4, 5, 6], [4, 2, 3]]
>>> b = [[[11, 22, 3], [12, 34, 6], [41, 2, 34], [198, 213, 536], [1198, 1123, 1156]], [[11, 22, 3], [42, 25, 64], [43, 45, 23]], [[3, 532, 23], [4, 5, 6], [98, 23, 56], [918, 231, 526]]]
>>> func(a,b)
True

帮助any：

>>> print any.__doc__
any(iterable) -> bool

Return True if bool(x) is True for any x in the iterable.
If the iterable is empty, return False.

使用集合交集获取所有公共元素：

>>> s_b = set(tuple(y) for x in b for y in x)
>>> s_a = set(tuple(x) for x in a)
>>> s_a & s_b
set([(4, 5, 6)])
于 2013-06-14T07:59:17.843 回答
3

用于itertools.chain.from_iterable先展平列表，然后简单地遍历它：

>>> B = [[[11, 22, 3], [12, 34, 6], [41, 2, 34], [198, 213, 536], [1198, 1123, 1156]], [[11, 22, 3], [42, 25, 64], [43, 45, 23]], [[3, 532, 23], [4, 5, 6], [98, 23, 56], [918, 231, 526]], [[11, 22, 3], [42, 54, 36], [41, 2432, 34]]]
>>> A = [[1, 2, 3], [4, 5, 6], [4, 2, 3]]
>>> for i in itertools.chain.from_iterable(B):
...     if i in A:
...             print True, i
... 
True [4, 5, 6]
于 2013-06-14T08:03:21.267 回答
1

使用 numpy：

import numpy
b=[ [], [] , [] ]
a = [[1, 2, 3], [4, 5, 6], [4, 2, 3]]
b[0] = [[11, 22, 3], [12, 34, 6], [41, 2, 34], [198, 213, 536], 
        [1198, 1123, 1156]]
b[1] = [[11, 22, 3], [42, 25, 64], [43, 45, 23]]
b[2] = [[3, 532, 23], [4, 5, 6], [98, 23, 56], [918, 231, 526]]

for p1 in a:
    for p2 in [ p for bb in b for p in bb]:
        v=numpy.linalg.norm(numpy.array(p1)-numpy.array(p2))
        if v == 0: print p1
于 2013-06-14T08:21:19.110 回答
0

试试这个代码：

a = [[1, 2, 3], [4, 5, 6], [4, 2, 3]]
b={}
b[0] = [[11, 22, 3], [12, 34, 6], [41, 2, 34], [198, 213, 536], [1198, 1123, 1156]]
b[1] = [[11, 22, 3], [42, 25, 64], [43, 45, 23]]
b[2] = [[3, 532, 23], [4, 5, 6], [98, 23, 56], [918, 231, 526]]
b[3] = [[11, 22, 3], [42, 54, 36], [41, 2432, 34]]

for i in b:
    for ii in i:
        if ii in a:
            return True

它有效，但我不确定它是否快。

于 2013-06-14T08:10:07.920 回答